Among conventional power converting apparatuses, there exists a below-mentioned power converting apparatus for photovoltaic power generation that converts DC power fed from a solar battery into AC power with three-phase outputs and delivers the AC power to a three-phase power system whose one phase is grounded with the power converting apparatus interconnected with the power system.
The power converting apparatus is provided with 3 sets of half-bridge inverters which are connected between output terminals of the solar battery, each half-bridge inverter being made up of two series-connected switching devices, single-phase inverters connected in series with AC output lines of the individual half-bridge inverters, and two series-connected capacitors for dividing a voltage of the solar battery, wherein output terminals of the single-phase inverters are connected to individual phases of the three-phase power system. The half-bridge inverters are operated at a rate of one pulse per half cycle and the individual single-phase inverters are controlled by pulse width modulation (PWM) so as to compensate for voltage insufficiencies with respect to a system voltage, whereby the power converting apparatus outputs the sums of outputs of the half-bridge inverters and the respective single-phase inverters. For this reason, it is possible to reduce an input DC voltage of the half-bridge inverters and a high voltage is not necessary to perform PWM control operation. Additionally, it is possible to reduce switching losses and lower the capacity of an output filter (refer to Patent Document 1, for example).